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๐ฌ Think about it
Fish breathe underwater — but how? Oxygen from the air dissolves into the water, just a little, and that keeps them alive. Open a cold soda and a warm soda; the warm one fizzes more because warm water holds less gas. Let's explore gases in water.
Do gases dissolve in water?
- Many gases, including oxygen, dissolve in water.
- Oxygen dissolves only to a small extent.
- This dissolved oxygen sustains all aquatic life.
- The mixture of gas in water is uniform.
Example:
Fish and water plants survive on the small amount of oxygen dissolved in water.
How does temperature affect the solubility of gases?
- The solubility of gases generally decreases as temperature rises.
- More oxygen dissolves in cold water.
- This gives aquatic life enough oxygen.
- When water warms up, less oxygen stays dissolved.
Solids in water
Gases in water
Solubility increases with temperature.
Solubility decreases with temperature.
More solid dissolves in hot water.
More gas dissolves in cold water.
Important Points
- Gases like oxygen dissolve in water, forming a uniform mixture.
- Dissolved oxygen keeps aquatic life alive.
- Gas solubility decreases as temperature increases.
Important Definitions
- Dissolved oxygen — the small amount of oxygen gas dissolved in water that sustains aquatic life.
๐ NCERT Question 8 — Analyse Fig. 9.25a and
Why does an unpeeled orange float while a peeled one sinks? Explain.
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